M31, Andromeda Galaxy, NGC 224,
Credit: NASA, ESA, J. Dalcanton, B.F. Williams, and L.C. Johnson (University of Washington), the PHAT team, and R. Gendler.
The largest NASA Hubble Space Telescope image ever assembled, this
sweeping bird's-eye view of a portion of the Andromeda galaxy (M31) is
the sharpest large composite image ever taken of our galactic next-door
neighbor. Though the galaxy is over 2 million light-years away, the
Hubble telescope is powerful enough to resolve individual stars in a
61,000-light-year-long stretch of the galaxy's pancake-shaped disk.
It's like photographing a beach and resolving individual grains of sand.
And, there are lots of stars in this sweeping view — over 100 million,
with some of them in thousands of star clusters seen embedded in the
disk.
This ambitious photographic cartography of the Andromeda galaxy
represents a new benchmark for precision studies of large spiral
galaxies that dominate the universe's population of over 100 billion
galaxies. Never before have astronomers been able to see individual
stars inside an external spiral galaxy over such a large contiguous
area. Most of the stars in the universe live inside such majestic star
cities, and this is the first data that reveal populations of stars in
context to their home galaxy.
Hubble traces densely packed stars extending from the innermost hub
of the galaxy, seen at left. Moving out from this central galactic
bulge, the panorama sweeps from the galaxy's central bulge across lanes
of stars and dust to the sparser outer disk. Large groups of young
blue stars indicate the locations of star clusters and star-forming
regions. The stars bunch up in the blue ring-like feature toward the
right side of the image. The dark silhouettes trace out complex dust
structures. Underlying the entire galaxy is a smooth distribution of
cooler red stars that trace Andromeda's evolution over billions of
years.
Because the galaxy is only 2.5 million light-years from Earth, it is a
much bigger target in the sky than the myriad galaxies Hubble
routinely photographs that are billions of light-years away. This means
that the Hubble survey is assembled together into a mosaic image using
7,398 exposures taken over 411 individual pointings.
The panorama is the product of the Panchromatic Hubble Andromeda
Treasury (PHAT) program. Images were obtained from viewing the galaxy
in near-ultraviolet, visible, and near-infrared wavelengths, using the
Advanced Camera for Surveys and the Wide Field Camera 3 aboard Hubble.
This cropped view shows a 48,000-light-year-long stretch of the galaxy
in its natural visible-light color, as photographed with Hubble's
Advanced Camera for Surveys in red and blue filters July 2010 through
October 2013.
The panorama is being presented at the 225th Meeting of the Astronomical Society in Seattle, Washington.
For additional information, contact:
Ray Villard
Space Telescope Science Institute, Baltimore, Md.
410-338-4514
villard@stsci.edu
Felicia Chou
NASA Headquarters, Washington, D.C.
202-358-0257
felicia.chou@nasa.gov
Julianne Dalcanton / Ben Williams
University of Washington, Seattle, Wash.
jd@astro.washington.edu / ben@astro.washington.edu
Source: HubbleSite
